[Docs] Remove misleading comment

The TikaImpl#parse method comment sounds like this method is only used
in the same package for testing, but AttachmentProcessor uses it outside
of testing, so we should remove this comment.

plugins/ingest-attachment/src/main/java/org/elasticsearch/ingest/attachment/TikaImpl.java

@@ -99,7 +99,6 @@ final class TikaImpl {
     /**
      * parses with tika, throwing any exception hit while parsing the document
      */
-    // only package private for testing!
     static String parse(final byte content[], final Metadata metadata, final int limit) throws TikaException, IOException {
         // check that its not unprivileged code like a script
         SpecialPermission.check();